Abstract
This paper proposes the use of a triple-line microstrip array for transmitting a magnetic field (|B1+|) into the whole body for magnetic resonance applications at ultra-high field strength, such as 7 T. We explored some technologies that can potentially be applied for whole-body 7 T magnetic resonance imaging, as there is ongoing research on this topic. The triple-line microstrip transmission line (t-MTL) array consists of 32 channels. Each channel has a t-MTL, comprising a main conductor line and two adjacent coupled lines. The adjacent lines are not connected directly to the source. This configuration resulted in increased intensity and a centered |B1+|-field. We compared the proposed structure and some reference radiofrequency (RF) transmitters, such as a patch antenna, using a magnet bore as a waveguide and a whole-body birdcage coil. We evaluated the performance of the t-MTL using cylindrical phantoms. We computed the |B1+|-field from each RF transmitter inside a 3D human model containing more than 200 tissues. We compared their uniformity and field intensity and proposed a t-MTL array that yielded better performance. The proposed design also showed a lower specific absorption rate compared with a patch antenna.
Highlights
We investigated a new design for a microstrip array for the whole body using a 7 T Magnetic resonance imaging (MRI) system and compared it with existing whole-body RF transmitters
The |B1+|-field was extracted from the human model after being excited using the patch antenna, birdcage coil, and the proposed array of triple-line microstrip transmission line (t-MTL)
The birdcage coil was excited in a quadrature mode, the tuning was made by using ring capacitors of 0.621 pF and leg capacitors of 65 pF, for which a S11 value of -20 dB was obtained before applying a matching circuit
Summary
Received: 24 November 2020 Accepted: December 2020 Published: December 2020. Magnetic resonance imaging (MRI) has been a useful tool for diagnosing health problems and studying the functions of the human body [1,2,3]. Studies on the use of MR scanners, such as 7 T, are increasing. As these strong main magnetic (|B0|)-field systems receive approval by the safety authorities for clinical use, some aspects of the radiofrequency (RF) transmission and hardware still need to be investigated, such as the use of whole-body systems [4,5,6,7]
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